Role of sulphur-heterocycles in medicinal chemistry: An update

Phosphorus-based organocatalysis encompasses several subfields that have undergone rapid growth in recent years. This Outlook gives an overview of its various aspects. In particular, we highlight key advances in three topics: nucleophilic phosphine catalysis, organophosphorus catalysis to bypass phosphine oxide waste, and organophosphorus compound-mediated single electron transfer processes. We briefly summarize five additional topics: chiral phosphoric acid catalysis, phosphine oxide Lewis base catalysis, iminophosphorane super base catalysis, phosphonium salt phase transfer catalysis, and frustrated Lewis pair catalysis. Although it is not catalytic in nature, we also discuss novel discoveries that are emerging in phosphorus(V) ligand coupling. We conclude with some ideas about the future of organophosphorus catalysis.

Phosphorus-Based Catalysis.

Natural sources display a high potential for the production of sustainable materials because of their exceptional structural and physical features, nontoxicity, biocompatibility, availability and cost-effectiveness. Nanostructured systems show high surface/volume ratio, and unusual electrical, mechanical, surface and magnetic properties. The preparation of heterogeneous nanocatalysts from natural resources has recently become increasingly attractive for researchers. The present overview discuses extensively and comprehensively the main natural sources used to prepare the new generation of safer and cheaper catalytic nanosystems. We place a significant emphasis on both the different synthetic strategies for the preparation of the Nature-inspired nanocatalyst and the role of the natural materials over the structural and morphological properties of the resulting nanocatalysts. The catalytic applications of nature-inspired materials were finally featured, highlighting the advantages of using nanotechnology and environmental resources as well as their potential towards the production of alternative energies.

Benign-by-design nature-inspired nanosystems in biofuels production and catalytic applications

Melamine-modified chitosan materials: An efficient and recyclable bifunctional organocatalyst for green synthesis of densely functionalized bioactive dihydropyrano[2,3-c]pyrazole and benzylpyrazolyl coumarin derivatives.

The present paper focuses on the synthesis of a novel hydrogel support by combining polysaccharides (chitosan NPs and dialdehyde cellulose nanowhiskers) and graphene oxide nanosheets to obtain a biocompatible material for catalytic applications. The hydrogel was synthesized via green chemistry processes and used as a support to prepare Pd nanoparticles. Finally, the hydrogel@Pd NPs was employed as the catalyst in the Mizoroki–Heck reaction to generate new C–C bonds. SEM analysis indicated that the hydrogel has macroporous morphology, which is in good correlation with its high crosslinking degree. The as-synthesized nanocomposite hydrogel exhibits beneficial properties such as ease of separation and excellent recyclability for at least six cycles without considerable loss in its activity. The yields of the products range from 81% to 98%. Additionally, this study provides the possibility to perform the Mizoroki–Heck reaction with aryl chloride in the presence of the as-prepared catalyst.

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Preparation of a novel palladium catalytic hydrogel based on graphene oxide/chitosan NPs and cellulose nanowhiskers

Ultrasound promoted rapid and green synthesis of thiiranes from epoxides in water catalyzed by chitosan-silica sulfate nano hybrid (CSSNH) as a green, novel and highly proficient heterogeneous nano catalyst.

Ultrasound-Promoted Mild, and Efficient Protocol for Three-Component Synthesis of 2,4,5-Trisubstituted Imidazoles Using Urea and PPh3 as the Sources of Nitrogen and Organocatalyst

The synthesis and characterization of chitosan-silica sulfate nano hybrid (CSSNH) as a novel and efficient heterogeneous nano catalyst involving acid-base bifunctional activity is described. The catalytic potency and activity of this eco-friendly catalyst was investigated in regioselective ring opening of epoxides with carboxylic acids to access structurally diverse 1,2-diol mono-esters in good to excellent yields. CSSNH catalyst was characterized using different microscopic and spectroscopic techniques encompassing scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption isotherm, and Fourier transform infrared spectroscopy (FT-IR). The green nature, cheapness, efficiency, ease of preparation, handling and reusability of this new catalyst makes this catalyst to be useful for green industrial processes.

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Chitosan-Silica Sulfate Nano Hybrid as a Novel and Highly Proficient Heterogeneous Nano Catalyst for Regioselective Ring Opening of Epoxides via Carboxylic Acids

The presilylation of purine and pyrimidine nucleobases as well as other related N-heterocycles with HMDS utilizing chitosan–silica sulfate nanohybrid (CSSNH) is described. CSSNH is proved to be a useful, highly efficient and eco-friendly heterogeneous nanohybrid catalyst for silylation of nucleobases. The presilylated nucleobases then underwent the reaction with different sources of carbon electrophiles to afford the desired N-alkyl-substituted derivatives in good-to-excellent yields. CSSNH exhibits several advantageous involving ease of handling and preparation, low cost, reusability and environmental benignity. These unique properties render the CSSNH to be an ideal candidate for use in green industrial processes.

Chitosan–silica sulfate nanohybrid: a highly efficient and green heterogeneous nanocatalyst for the regioselective synthesis of N-alkyl purine, pyrimidine and related N-heterocycles via presilylated method

Toxicopathological effects of herbs have always been a major concern. There is scant information available about the toxicopathological effects of Calotropis procera (C. procera) in the fetus. Since the chick embryo is a suitable preclinical model to evaluate the toxicopathological effects of chemicals, the objective of this study is to evaluate the lesions of various dosages of C. procera using a chick embryonic model. Fertile chicken eggs were divided into three equal treatment groups; phosphate buffered saline-injected group and C. procera-injected groups whose individuals were treated with C. procera extract at dosages of 50 or 100 mg/kg egg-weight. Embryos were re-incubated post-treatment and allowed to develop until day 18, after which they were examined for macroscopic and microscopic lesions. Although the embryos which were treated with 50 mg/kg egg-weight of C. procera extract macroscopically were normal as well as the controls, those treated with 100 mg/kg egg-weight were stunted and under developed. Microscopic evaluations showed that in embryos treated with 100 mg/kg egg-weight of C. procera, the brain was congested, and severe dilation of central veins and sinusoids as well as hepatocellular degeneration was occurred in liver. Moreover, the kidney and lung were under-developed, but the structure of the heart was normal. Based on our findings, C. procera at dosage of 100 mg/kg is toxic to the chick embryo or/maybe to human fetus during growing period. Further studies are needed to clarify the toxic effects of this plant on the development of fetus.

Mohammad Amin Piltan

Papers

Ultrasound promoted rapid and green synthesis of thiiranes from epoxides in water catalyzed by chitosan-silica sulfate nano hybrid (CSSNH) as a green, novel and highly proficient heterogeneous nano catalyst.

Ultrasound-Promoted Mild, and Efficient Protocol for Three-Component Synthesis of 2,4,5-Trisubstituted Imidazoles Using Urea and PPh3 as the Sources of Nitrogen and Organocatalyst

Chitosan-Silica Sulfate Nano Hybrid as a Novel and Highly Proficient Heterogeneous Nano Catalyst for Regioselective Ring Opening of Epoxides via Carboxylic Acids

Chitosan–silica sulfate nanohybrid: a highly efficient and green heterogeneous nanocatalyst for the regioselective synthesis of N-alkyl purine, pyrimidine and related N-heterocycles via presilylated method

Evaluation of the toxicopathological lesions of Calotropis procera using a chick embryonic model